1. Field of the Invention
The present invention relates to a temperature sensor.
2. Description of Related Art
Motor vehicles are provided with temperature sensors for various uses. For example, the temperature sensor described in Japanese Patent Application Laid-open No. 2013-72769 is used for detecting the temperature in a hydrogen tank of a fuel cell vehicle to control a filling rate of hydrogen into the hydrogen tank. The temperature sensor is required to be resistant to a high pressure occurring in the hydrogen tank during filling the hydrogen tank. Accordingly, the temperature sensor is provided with a sealing supplementary body to prevent a sealing glass which covers a thermo-sensitive element from being damaged. The sealing supplementary body is formed with a pair of insertion holes. A pair of lead wires electrically connected to the thermo-sensitive element can be inserted into the insertion holes.
However, the conventional temperature sensor described above has the following problems. There is a gap between the insertion hole of the sealing supplementary body and the lead wire. If melted glass flows in to the gap at the time of forming the sealing glass, a thin glass layer is formed within the gap. This thin glass layer is lower in strength than the sealing glass. Accordingly, there is a concern that the thin glass layer may be broken due to thermal shock and pressure occurring in the hydrogen tank. Further, the sealing glass may be broken as a result of breakage of the thin glass layer. Recently, since the filling time of a hydrogen tank is required to be shortened, the thermal shock at the start of filling of the hydrogen tank and the pressure within the hydrogen tank during filling of the hydrogen tank tend to increase. Therefore, there is a demand to provide a temperature sensor having an increased strength. Incidentally, the thin glass layer may pose a problem for uses other than hydrogen tanks, which require high resistivity to pressure, thermal shock or vibration.